在单个查询中使用多个连接

Question

我正在尝试修改以前的查询以删除 where 部分并使用连接，但在执行此操作时出现错误。我已尝试阅读 Oracle 文档，但没有找到任何内容来修复我的错误。

上一个查询：

SELECT DISTINCT 
    CLI.IDCLI, CLI.NOMCLI,CLI.PRENOMCLI
FROM
    LIVRAISON LIV, LIVRAISON LIV1, CLIENT CLI, COMMANDE COM, CLIENT CLI1, COMMANDE COM1
WHERE 
    CLI.IDCLI = COM.IDCLI
    AND COM.IDCOM = LIV.IDCOM
    AND CLI1.IDCLI = COM1.IDCLI
    AND COM1.IDCOM = LIV1.IDCOM
    AND LIV.DATELIV = LIV1.DATELIV
    AND LIV.IDLIV = LIV1.IDLIV
    AND CLI1.NOMCLI = 'MARTIN'
    AND CLI.IDCLI != CLI1.IDCLI
ORDER BY 
    CLI.IDCLI ASC;

新查询和错误：

SQL> SELECT DISTINCT CLI.IDCLI, CLI.NOMCLI,CLI.PRENOMCLI
  2  FROM LIVRAISON LIV      NATURAL JOIN LIVRAISON LIV1
  3                          INNER JOIN COMMANDE COM       ON COM.IDCOM=LIV.IDCOM,
  4        LIV1              INNER JOIN COMMANDE COM1      ON LIV1.IDCOM=COM1.IDCOM,
  5        CLIENT CLI        INNER JOIN COM                ON CLI.IDCLI=COM.IDCOM,
  6        COM1              INNER JOIN CLIENT CLI1        ON CLI1.IDCLI=COM1.IDCLI
  7  WHERE CLI1.NOMCLI='MARTIN'
  8  AND CLI.IDCLI!= CLI1.IDCLI
  9  ORDER BY CLI.IDCLI ASC;
      COM1              INNER JOIN CLIENT CLI1        ON CLI1.IDCLI=COM1.IDCLI
      *
ERROR at line 6:
ORA-00942: table or view does not exist

Answer 1

避免自然连接，除非您是经验丰富的连接魔术专家。

不要将旧的逗号语法与连接语法混合使用。

使用独特的 table 别名。

SELECT DISTINCT
  CLI.IDCLI, 
  CLI.NOMCLI, 
  CLI.PRENOMCLI
FROM LIVRAISON LIV
JOIN LIVRAISON LIV2 ON LIV2.DATELIV = LIV.DATELIV
                   AND LIV2.IDLIV   = LIV.IDLIV
JOIN COMMANDE  COM  ON COM.IDCOM    = LIV.IDCOM
JOIN CLIENT    CLI  ON CLI.IDCLI    = COM.IDCLI
JOIN COMMANDE  COM2 ON COM2.IDCOM   = LIV2.IDCOM
JOIN CLIENT    CLI2 ON CLI2.IDCLI   = COM2.IDCLI
WHERE CLI2.NOMCLI = 'MARTIN'
  AND CLI.IDCLI  != CLI2.IDCLI
ORDER BY 
  CLI.IDCLI ASC;

在单个查询中使用多个连接

use multiple join in a single query

sql

inner-join

alias